Expansion drill



Mar'cblm. CIRGUNDERsON f .2,193,721-

EXPANSION DRILL Filed Apyil s., 1939 A' GR.GunZerJozz 3mm www 25 formedin the cutter part I6 of each blade member I5 so as to thereby form anadjustable blade extension means to limit the extension of the blademembers I5 relative to the shank I 8. In the present instance, thecoupling parts I of the blades I5 are pivotally mounted on a common pin26, which extends through the parts I I a of shank ID and has theopposite ends thereof upsent as at 2l. As shown in Figure 2, the twocutouts I4 are disposed in spaced apart parallel relation, whereas inFigure 4 a slightly modified form of this construction is disclosed, theshank Illa being similar to every detail to the shank Iil with theexception that the outer end thereof is provided with a pair of slotsMa, which at their inner portions communicate one with the other and thetwo blades or bits I5o have their bearing portions Ia disposed in faceabutting relation. In this instance, a tapered pin 2Go, is extendeddiametrically across the shank lita and through the two slots Ma. rTheopposite ends of the pin or shaft 26a may be upset or enlarged toprevent endwise movement thereof.

The sleeve 24 is locked in adjusted position on the shank I by means ofa spring-pressed pawl 23 provided with a bill 29 engaging in alongitudinally extending groove or channel 3B formed in the part II ofthe shank I5. The pawl 2S is provided with an extension or iinger piece3i projecting into a cutout 32 provided in the sleeve Z4 so that thepawl 23 may be rocked on the pivot 33 against the tension of the spring34. 'Ihe pawl A2li is preferably countersunk in a suitable recessprovided in the upper or outer end of the sleeve 24.

In the use and operation of this drill, the hole I3 is initially formedon the body of material I2 by any suitable form of drill, then the drillcomprising the shank IU and the blades or bits I5 is inserted in theopening I3. Initially the two bits or blades I5 are disposed incollapsed or retracted position, as shown in dotted lines in Figure 1.If desired a hammer or impact device may be engaged with the opposite orinner end of the shank I0. Where a hammer or impact device is used theimpact on the shank Ill will tend to spread the two bit members I5 apartat the bottom or inner end of the opening or hole I3. This action willcontinue until the two bit members I5 swing laterally to the limitpermitted either by the abutments 22 or the bit controlling sleeve 24.When the two bits or blades I5 are in their extended position, similarto that shown in full lines in Figure l, finther impact or rotation ofthe shank IG and the bits or blades I5 will enlarge the bottom or innerend of the opening I3. In this manner a substantially large diameterpocket will be provided at the inner end of the opening I3 so as toadmit of the insertion of either a toggle bolt or, if desired, blastingmaterial may be inserted in the enlarged pocket and the outer portion ofthe opening I3 closed in the usual manner.

It has been found in actual practice that an enlarged pocket or recessformed by this drill will facilitate any blasting operations as thispocket will permit of a larger quantity of blasting material beingpositioned at the inner end of the hole and eliminate the action of anyblasting material which at present extends toward the outer end of theopening I3.

Where the condition of the material permits,

the drill comprising of shank I0 and the two bits I5 may be connected toor mounted in a chuck or other rotating means so that the bits I5 may berotated within the opening I3 at the same time that these bits are movedinwardly of the opening I3. By providing the abutments 22 at the outerend of the shank I0 and also providing an arcuate or substantially roundsocket I9 for the bearing portion I9 of each bit or blade I5, the strainapplied to the shank IU by an impact device or rotating means is takenoI of the pin 26. In this manner the pin 26 will not be sheared off byreason of any strain applied to the shank I 0 and the bits I5.

Where it is desired to enlarge the pocket at the inner end of theopening I3 to a size substantially smaller than the complete extensionof the two bits or blades I5 the sleeve 24 is threaded outwardly so thatthe outer end of the sleeve 24 forms an adjustable abutment engageablein the recesses 25 of each blade I5.

What I claim is:

l. In an expansion bit of that type including a pair of oppositelydisposed blades each having a substantially circular inner portion and acutter portion having a shoulder at its inner end, said bit comprising ashank having a threaded part intermediate .its ends and a non-threadedpart extended outwardly from the outer end of said threaded part, saidthreaded part having its outer terminal portion formed withdiametrically opposed substantially semi-circular cavities adapted toreceive the inner portions of the blades, said non-threaded part beingformed with a pair of oppositely disposed blade receiving cutouts inopposite sides thereof opening at its outer end and at spaced portionsof its periphery, said cavities opening into said cutouts, each of saidcutouts including an inner end wall formed with a curved part providinga continuation of the wall of a cavity adapted for engaging the edge ofan inner portion of a blade, each of cutouts having its inner wallformed with an inclined part disposed at an obtuse angle to the saidother part and constituting an abutment for engagement by the shoulderof a blade, and means extending through said non-threaded part andcommon to inner portions of said blades for pivotally connecting thelatter to the shank.

2. The invention as set forth in claim l having the threaded part of theshank formed lengthwise thereof with a groove, an adjustable controllingmember for the blades threadedly engaging with the threaded part of theshank, and

spring-controlled means carried by said member and correlating with saidgroove for latching said member in adjusted position.

3. In an expansion bit of that type including a pair of controllableoppositely disposed extendible and retractible blades, the combinationof a shank provided intermediate its ends with a threaded part and anon-threaded part extending outwardly from the outer end of saidthreaded part, means for pivotally connecting the blades to saidnon-threaded part, said threaded part being formed lengthwise thereofwith a groove, an adjustable controlling member for said bladesthreadedly engaging with the said threaded part, and spring-controlledmeans carried by said member and correlating with said groove forlatching said member in adjusted position.

CHESLEY RAY GUNDERSON.

